WITH horrific events rendered as black screwball comedy, “Running With Scissors” plays roughly as if Wes Anderson’s whimsical script for “The Royal Tenenbaums” was directed by the darker Paul Thomas Anderson (“Magnolia”).

Less than ideally focused but with terrific performances – especially by the Oscar-baiting Annette Bening as a monster mom – this is a compulsively watchable movie best enjoyed by forgetting that it’s supposedly based on actual events in the life of novelist Augusten Burroughs.

“Nobody’s going to believe me anyway,” says the movie Augusten in the opening narration, which may be the understatement of the year as writer-director Ryan Murphy (TV’s “Nip/Tuck”) cuts together one incredible episode following another.

After his alcoholic father, Norman (Alec Baldwin), walks out on his pill-popping, feminist poet manqué mother, Deirdre (Bening), in the 1970s, she begins dabbling in lesbianism.

Deirdre sends Augusten (newcomer Joseph Cross), a wide-eyed 16-year-old with artistic sensibilities of his own, to live with her shrink, a sort of dementedly benevolent Santa Claus named Dr. Finch (Brian Cox) who divines the future from his bowel movements.

Also living in the good doctor’s rubble-strewn Gothic manse is his near-catatonic wife (Jill Clayburgh), devoted to cat kibble and reruns of “Dark Shadows,” and two daughters.

Hope (Gwyneth Paltrow, in a variation on her “Tenenbaums” role), is a depressive who makes her decisions by choosing random words from the Bible; livelier younger sis Natalie (Rachel Evan Wood) unsuccessfully attempts to seduce Augusten with an electroshock therapy machine.

Our precocious adolescent hero is more taken with Dr. Finch’s adopted son Neil, a 35-year-old schizophrenic former patient who lives in the garage.

Played with dark charm by Joseph Fiennes in his most visible role since “Shakespeare in Love,” pedophile Neil is practically a walking advertisement for the North American Man-Boy Love Association.

Anyway, Augusten’s budding sexuality is presented as the least of his problems.

While Murphy never manages to make this crazy quilt dramatically credible, he does hit the mark for laughs and has written some juicy scenes for his excellent cast.

Bening does her best work here since “American Beauty,” with Cox, Baldwin and Clayburgh not far behind.

“Running With Scissors” gets a bit winded as it approaches the two-hour mark, but it’s surprisingly nimble for a film that seems afraid to cut too deeply.